Cardiovascular disease (CVD) is the leading cause of death and disabilities worldwide, as well as in the United States2. It accounts for 34.4 percent of the 2.4 million annual deaths in US, and leads to the most health disparities and rising healthcare costs. It is known that endothelial dysfunction represents a key step in the initiation and maintenance of CVD5. Although studies showed that multiple factors, including circulating inflammatory cytokines, reactive oxygen species, oxidized LDL (low density lipoprotein), autoantibodies and traditional risk factors directly and indirectly cause endothelial cell dysfunction, and eventually lead to CVD, our knowledge of endothelial cell regulation is still insufficient for the development of an effective therapeutics to control this disease. Better understanding of the molecular mechanism, by which endothelial cells functions under biological and pathologic conditions, is required to improve the treatment of CVDs. During our previous study we found a new molecule that played a critical role in endothelial cells for angiogenesis that has not be described previously -- adenosine deaminase acting on RNA1 (ADAR1). This proposal is to define the function and mechanism of ADAR1 in endothelial cells. It is known that ADAR1 is an essential protein for posttranscriptional RNA process. It regulates gene functions through changing the protein codon and modifying microRNA biogenesis. It also regulates cytoplasmic RNA signaling pathways to suppress innate immune and stress responses. Knockout ADAR1 specifically in endothelial cells dramatically elevated blood pressure, significantly impaired angiogenesis in hind limb ischemic animal models. In this proposed study, we will analyze the newly generated endothelial specific knockout mice of ADAR1, determine the gene expression pattern of ADAR1 and find the potential association of ADAR1 expression with the functional status of endothelial cells. ADAR1 expression levels in young healthy animal, aged and diseased animal, such as diabetic animals will be determined. We will also look into the relationship of ADAR1 and the inflammatory cytokines, reactive oxygen species, oxidized LDL. We will also determine the effect of ADAR1 in angiogenesis under ischemia condition by using the hind limb ischemic mouse model. Based on our preliminary finding that coviolin-1 is regulated by ADAR1, we will try to reveal the mechanism of ADAR1 by which it regulate blood vessel function and involves in blood vessel diseases.